Pressure gas-activated casting apparatus for casting cast iron (gray iron) and malleable cast iron are generally known and have been widely used. To a much lesser degree, such casting apparatus have also been used for casting iron treated with magnesium. In many cases, these casting apparatus use blend operations, i.e. cast iron or malleable cast iron are cast along with iron that is treated with magnesium.
Casting with such types of pressure gas casting apparatus requires precise control operations of the furnace pressure, meaning that the pressure is increased and decreased by means of control devices having small cross sections. It is known that magnesium from the rapidly cooling inert gas flowing out of the furnace condenses and is deposited in the piping of the control and regulatory system, particularly where the flow passages narrow, such as in valves, apertures, and the like, particularly when larger proportions of magnesium-treated iron are cast in relation to the total volume of iron. Because of their high degree of flammability and their tendency to explode, these deposits represent safety risks for the maintenance personnel when the equipment if periodically cleaned and serviced. This danger particularly exists when portions of the deposited magnesium are dislodged during the maintenance and cleaning work. Especially thick deposits lead to explosions. Thus, these thick deposits cannot be allowed to form. Only the external coating of such a thick deposit can be oxidized. Once that coating is removed, an explosion results.